Base screenshare layers on TemporalReferences.

webrtc/modules/video_coding/codecs/vp8/default_temporal_layers.cc

 /* Copyright (c) 2013 The WebRTC project authors. All Rights Reserved.
 *
 *  Use of this source code is governed by a BSD-style license
 *  that can be found in the LICENSE file in the root of the source
 *  tree. An additional intellectual property rights grant can be found
 *  in the file PATENTS.  All contributing project authors may
 *  be found in the AUTHORS file in the root of the source tree.
 */
 
 #include "webrtc/modules/video_coding/codecs/vp8/default_temporal_layers.h"
@@ skipping 27 matching lines @@
                          golden,
                          arf,
                          (extra_flags & kLayerSync) != 0,
                          (extra_flags & kFreezeEntropy) != 0) {}
 
 TemporalReferences::TemporalReferences(TemporalBufferUsage last,
                                        TemporalBufferUsage golden,
                                        TemporalBufferUsage arf,
                                        bool layer_sync,
                                        bool freeze_entropy)
-    : reference_last((last & kReference) != 0),
+    : drop_frame(last == kNone && golden == kNone && arf == kNone),
+      reference_last((last & kReference) != 0),
       update_last((last & kUpdate) != 0),
       reference_golden((golden & kReference) != 0),
       update_golden((golden & kUpdate) != 0),
       reference_arf((arf & kReference) != 0),
       update_arf((arf & kUpdate) != 0),
       layer_sync(layer_sync),
       freeze_entropy(freeze_entropy) {}
 
 namespace {
 
@@ skipping 180 matching lines @@
   cfg->ts_number_layers = num_layers_;
   cfg->ts_periodicity = temporal_ids_.size();
   memcpy(cfg->ts_layer_id, &temporal_ids_[0],
          sizeof(unsigned int) * temporal_ids_.size());
 
   new_bitrates_kbps_ = rtc::Optional<std::vector<uint32_t>>();
 
   return true;
 }
 
-int DefaultTemporalLayers::EncodeFlags(uint32_t timestamp) {
+// TODO(pbos): Name method so that it's obvious that it updates state.

[sprang_webrtc, 2017/03/26 12:20:08]

Not sure "get" makes it obvious state is changed either. Maybe
UpdateLayerConfig() or NextLayerConfig() or something along those lines?

[pbos-webrtc, 2017/03/27 16:31:07]

I like update. Thanks.

+TemporalReferences DefaultTemporalLayers::GetLayerConfig(uint32_t timestamp) {
   RTC_DCHECK_GT(num_layers_, 0);
   RTC_DCHECK_LT(0, temporal_pattern_.size());
+  return temporal_pattern_[++pattern_idx_ % temporal_pattern_.size()];
+}
+
+int TemporalLayers::EncodeFlags(uint32_t timestamp) {
+  TemporalReferences references = GetLayerConfig(timestamp);
+  if (references.drop_frame)
+    return -1;
+
   int flags = 0;
-  // TODO(pbos): Move pattern-update out of EncodeFlags. It's not obvious that
-  // EncodeFlags() is non-const.
-  const TemporalReferences& references =
-      temporal_pattern_[++pattern_idx_ % temporal_pattern_.size()];
 
   if (!references.reference_last)
     flags |= VP8_EFLAG_NO_REF_LAST;
   if (!references.update_last)
     flags |= VP8_EFLAG_NO_UPD_LAST;
   if (!references.reference_golden)
     flags |= VP8_EFLAG_NO_REF_GF;
   if (!references.update_golden)
     flags |= VP8_EFLAG_NO_UPD_GF;
   if (!references.reference_arf)
     flags |= VP8_EFLAG_NO_REF_ARF;
   if (!references.update_arf)
     flags |= VP8_EFLAG_NO_UPD_ARF;
   if (references.freeze_entropy)
     flags |= VP8_EFLAG_NO_UPD_ENTROPY;
 
   return flags;
 }
 
 void DefaultTemporalLayers::PopulateCodecSpecific(
-    bool base_layer_sync,
+    bool frame_is_keyframe,
     CodecSpecificInfoVP8* vp8_info,
     uint32_t timestamp) {
   RTC_DCHECK_GT(num_layers_, 0);
 
   if (num_layers_ == 1) {
     vp8_info->temporalIdx = kNoTemporalIdx;
     vp8_info->layerSync = false;
     vp8_info->tl0PicIdx = kNoTl0PicIdx;
   } else {
-    if (base_layer_sync) {
+    if (frame_is_keyframe) {
       vp8_info->temporalIdx = 0;
       vp8_info->layerSync = true;
     } else {
       vp8_info->temporalIdx = CurrentLayerId();
       TemporalReferences temporal_reference =
           temporal_pattern_[pattern_idx_ % temporal_pattern_.size()];
 
       vp8_info->layerSync = temporal_reference.layer_sync;
     }
     if (last_base_layer_sync_ && vp8_info->temporalIdx != 0) {
       // Regardless of pattern the frame after a base layer sync will always
       // be a layer sync.
       vp8_info->layerSync = true;
     }
     if (vp8_info->temporalIdx == 0 && timestamp != timestamp_) {
       timestamp_ = timestamp;
       tl0_pic_idx_++;
     }
-    last_base_layer_sync_ = base_layer_sync;
+    last_base_layer_sync_ = frame_is_keyframe;
     vp8_info->tl0PicIdx = tl0_pic_idx_;
   }
 }
 
 TemporalLayers* TemporalLayersFactory::Create(
     int simulcast_id,
     int temporal_layers,
     uint8_t initial_tl0_pic_idx) const {
   TemporalLayers* tl =
       new DefaultTemporalLayers(temporal_layers, initial_tl0_pic_idx);
   if (listener_)
     listener_->OnTemporalLayersCreated(simulcast_id, tl);
   return tl;
 }
 
 void TemporalLayersFactory::SetListener(TemporalLayersListener* listener) {
   listener_ = listener;
 }
 
 }  // namespace webrtc